The ornamental design for a spongecaddy, as shown and described.
FIG. 1 is a perspective view of a sponge caddy showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken-lines represent portions of the caddy which form no part of the claimed design, and the areas between broken-away portions also form no part of the claimed design.